Seconds From Disaster

No country needs an effective earthquake-warning system more than Japan, with its dizzyingly dense population and constant barrage of earthquakes (more than a thousand of them strong enough to feel every year). By this spring they may finally have one—the first national system in the world.

If all goes according to plan, a network of nearly 1,000 seismometers deployed around the archipelago will pick up "P-waves," the fast-moving seismic grumbles that herald major quakes. A Japan Meteorological Agency computer will then determine the quake's epicenter and strength, providing a warning of up to 30 seconds. And not just any warning: In addition to general broadcast alerts, a server system will beam the timing and expected strength of the coming quake directly into households as well as to railway operators, fire departments, and other key institutions. Closer to the epicenter the warning time may be much shorter, but in a major quake, seconds can mean the difference between life and death if they are used to shut off the gas or pull over to the side of the road.

The detector also has a possible dark side. Authorities now worry that false alarms or news of an impending disaster could cause panic. On the crowded streets of Tokyo, that could be a public-health hazard in its own right. "We have to be careful how we use it," says Shinya Tsukada, a senior scientific officer at the Japan Meteorological Agency. "The information is very powerful, but there is a scientific limit to its accuracy."

Still, something must be done. Despite its tiny size, Japan is the target of 20 percent of all quakes that rate a 6 or higher on the Richter scale. A recent government study estimated that $955 billion worth of damage and 11,000 deaths could result from a magnitude 7.3 earthquake directly under the northern part of Tokyo Bay—a monster quake many seismologists believe is long overdue.